FIG. 8 schematically shows a conventional method for manufacturing an optical display unit to be incorporated into a liquid crystal display device. First, an optical film manufacturer produces a belt-shaped sheet material, which includes an optical film, in the form of a roll (#1). Specific processes for the manufacture thereof are known, and therefore a description thereof is omitted. The roll of the belt-shaped sheet material typically includes a raw polarizing plate, a raw retardation plate, or a raw laminated film of a polarizing plate and a retardation plate for use in the production of liquid crystal displays. The long material is then stamped into pieces of the sheet material having a shape according to the size of an optical display unit to which each piece will be bonded (#2). Each piece of the sheet material (optical film) obtained by the stamping is then subjected to an appearance inspection (#3). Examples of the inspection method include a visual inspection for defects and an inspection using a known defect inspection apparatus. The term “defect” typically means fouling of the surface or the inside, scratches, a foreign substance-containing defect with a special shape such as a dented and twisted shape (also called “knick”), bubbles, foreign substances, etc. The finished product is then inspected (#4). The finished product inspection is performed according to more strict quality criteria than those for the appearance inspection to determine whether the product is non-defective. Subsequently, the four end faces of each piece of the sheet material are worked (#5). The working is performed to prevent the pressure-sensitive adhesive or any other material from coming out of the end faces in transit. Each piece of the sheet material is then subjected to clean packaging in a clean room environment (#6). Subsequently, packaging for transportation (transport packaging) is performed (#7). Each piece of the sheet material manufactured as described above is transported to a panel processing manufacturer.
The panel processing manufacturer unpacks the piece of the material sheet transported (#11). An appearance inspection is then performed to check whether scratches, stains or other defects are produced in transit or during unpacking (#12). The piece of the sheet material determined to be non-defective by the inspection is then transferred to the next step. This appearance inspection may be omitted in some cases. The optical display unit (such as a glass substrate unit with a sealed liquid crystal cell) to which the piece of the sheet material will be bonded is previously manufactured and cleaned before the bonding step (#13).
The piece of the sheet material and the optical display unit are bonded together (#14). The release film is peeled off from the piece of the sheet material so that the pressure-sensitive adhesive can be left, and the bonding surface of the pressure-sensitive adhesive layer is attached to one side of the optical display unit. The other side of the optical display unit may also be subjected to a similar bonding process. The optical films to be bonded to both sides of the optical display unit may have the same structure or different structures. The optical display device having the bonded optical film is then subjected to an inspection and a defect inspection (#15). The optical display device determined to be non-defective by the inspection is transferred to an implementing process (#16). On the other hand, the optical display device determined to be defective is subjected to a reworking process (#17). In the reworking process, the optical film is peeled off from the optical display unit. A new optical film is bonded to the optical display unit having undergone the reworking process (#14).
The manufacturing process described above particularly requires the steps of working the end faces, packaging each piece of the sheet material, and unpacking the material, because the optical film manufacturer and the panel processing manufacturer are located at different places. However, such a multi-step process has the problem of an increase in manufacturing cost. There are also problems in which scratches, dust, stains, and the like can be caused by the multi-step process or the transportation so that an inspection process can be necessary, and problems in which different types of sheet materials must be carried and managed.
Japanese Patent Application Laid-Open (JP-A) No. 2007-140046 (Patent Document 1) discloses a method to solve the problems. A system by the method includes means for drawing and feeding a belt-shaped sheet material from a roll of the belt-shaped sheet material including an optical film to be used as a component of an optical display device, means for detecting defects in the belt-shaped sheet material drawn from the feeding means, means for cutting the belt-shaped sheet material into sheet material pieces based on the result of the detection by the detecting means, means for transporting each sheet material piece cut by the cutting means to a bonding process, and means for bonding the transported sheet material piece to an optical display unit as a component of the optical display device, wherein the respective means are arranged on a continuous production line. In this system, the belt-shaped sheet material including the optical film can be directly cut into the desired size, and the cut piece of the sheet material can be directly bonded to the optical display unit. According to a conventional technique, the belt-shaped sheet material is stamped into pieces, and the stamped sheet material pieces are each carefully packaged and delivered to a panel processing manufacturer. According to this system, however, a roll of the belt-shaped sheet material can be directly packaged and delivered.